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On determination of the geoid from measured gradients of the Earth's gravity field potential / Pavel Novák in Earth-Science Reviews, vol 221 (October 2021)  

Public [article]  inEarth-Science Reviews > vol 221 (October 2021) . - n° 103773 Titre : On determination of the geoid from measured gradients of the Earth's gravity field potential Type de document : Article/Communication Auteurs : Pavel Novák, Auteur ; Michal Šprlák, Auteur ; Martin Pitoňák, Auteur Année de publication : 2021 Article en page(s) : n° 103773 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] champ de pesanteur terrestre [Termes IGN] géoïde terrestre [Termes IGN] gradient de gravitation [Termes IGN] modèle mathématique [Termes IGN] modèle stochastique [Termes IGN] précision centimétrique [Termes IGN] problème des valeurs limites Résumé : (auteur) The geoid is an equipotential surface of the static Earth's gravity field which plays a fundamental role in definition of physical heights related to the mean sea level (orthometric heights) in geodesy and which represents a reference surface in many geoscientific studies. Its determination with the cm-level accuracy or better, in particular over dry land, belongs to major tasks of modern geodesy. Traditional data and underlined theory have significantly been affected in recent years by rapid advances in observation techniques. This study reviews gradients of the disturbing gravity potential, both currently available and foreseen, and systematically discusses mathematical models for geoid determination based on gradient data. Fundamentals required for geoid definition and its estimation from measured potential gradients are shortly reviewed at the beginning of the text. Then particular mathematical models based on solutions to boundary-value problems of the potential theory, which include both integral transforms and integral equations, are formulated. Properties of respective integral kernel functions are demonstrated and discussed. With the new mathematical models introduced, new research topics are opened which must be resolved in order to allow for their full-fledged applicability in geoid modelling. Stochastic modelling is also discussed which estimates gradient spatial resolution and accuracy required for geoid modelling with the cm-level accuracy. Results of stochastic modelling suggest that the cm-geoid can be estimated using available gradient data if related problems, namely reduction of gradient data for gravitational effects of all masses outside the geoid and their downward continuation, are solved at the same level of accuracy. Numéro de notice : A2021-944 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1016/j.earscirev.2021.103773 Date de publication en ligne : 14/09/2021 En ligne : https://doi.org/10.1016/j.earscirev.2021.103773 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=99756 [article]

The Iranian height datum offset from the GBVP solution and spirit-leveling/gravimetry data / Amir Ebadi in Journal of geodesy, vol 93 n° 8 (August 2019)  

Public [article]  inJournal of geodesy > vol 93 n° 8 (August 2019) . - pp 1207 - 1225 Titre : The Iranian height datum offset from the GBVP solution and spirit-leveling/gravimetry data Type de document : Article/Communication Auteurs : Amir Ebadi, Auteur ; Alireza A. Ardalan, Auteur ; Roohollah Karimi, Auteur Année de publication : 2019 Article en page(s) : pp 1207 - 1225 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] analyse de variance [Termes IGN] champ de pesanteur terrestre [Termes IGN] compensation par moindres carrés [Termes IGN] géoïde terrestre [Termes IGN] Iran [Termes IGN] levé gravimétrique [Termes IGN] modèle de géopotentiel [Termes IGN] potentiel de pesanteur terrestre [Termes IGN] problème des valeurs limites [Termes IGN] réseau altimétrique local [Termes IGN] réseau altimétrique national Résumé : (auteur) The gravity potential of the zero point of the Iranian height datum (IRHD) is determined as well as the IRHD offset from a global geoid. For this purpose, the geodetic boundary value problem (GBVP) solution based on the remove–compute–restore (RCR) technique is used. In the RCR technique, a global geopotential model (GGM) is required as a reference to remove and restore the long wavelengths of the gravity field. Since the GGMs do not have adequate accuracy over Iran, the IRHD offset is not precisely estimated by the GBVP solution. In this study, aiming to improve the latter, a combination solution based on the GBVP approach and spirit-leveling/gravimetry (LG) data, called the GBVP_LG solution, is proposed. To obtain the GBVP_LG solution, gravity potential obtained from the GBVP solution and the gravity potential differences derived from the LG data are used as two types of observations in a least-squares adjustment. The proper relative weight matrices are determined using the variance component estimation method. To evaluate the proposed method, the gravity potential differences between the start and end points of several check-lines in the leveling network derived from the GBVP and GBVP_LG solutions are compared with those of the LG data. The results show that the dependency of the GBVP_LG solution on the reference model used is much less than that of the GBVP solution. In addition, the results indicate that the GBVP_LG solution has a 42% improvement with respect to the GBVP solution in terms of root-mean-square error. As a result of the GBVP_LG solution, the gravity potential of the IRHD zero point is estimated equal to WIRHD0=62,636,855.89±0.16m2/s2. Therefore, the IRHD offset with respect to the geoid defined by W0=62,636,853.4m2/s2 is obtained equal to −25.4±1.6cm, which means that the IRHD is 25.4 cm below the geoid. Numéro de notice : A2019-385 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-019-01237-x Date de publication en ligne : 12/02/2019 En ligne : https://doi.org/10.1007/s00190-019-01237-x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=93464 [article]

On the assimilation of absolute geodetic dynamic topography in a global ocean model: impact on the deep ocean state / Alexey Androsov in Journal of geodesy, vol 93 n° 2 (February 2019)  

Public [article]  inJournal of geodesy > vol 93 n° 2 (February 2019) . - pp 141 - 157 Titre : On the assimilation of absolute geodetic dynamic topography in a global ocean model: impact on the deep ocean state Type de document : Article/Communication Auteurs : Alexey Androsov, Auteur ; Lars Nerger, Auteur ; Reiner Schnur, Auteur ; Alberta Albertella, Auteur ; Reiner Rummel, Auteur ; et al., Auteur Année de publication : 2019 Article en page(s) : pp 141 - 157 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] assimilation des données [Termes IGN] circulation océanique [Termes IGN] données altimétriques [Termes IGN] données CHAMP [Termes IGN] données GOCE [Termes IGN] données GRACE [Termes IGN] filtre de Kalman [Termes IGN] geoïde marin [Termes IGN] géoïde terrestre [Termes IGN] hauteurs de mer [Termes IGN] modèle de simulation [Termes IGN] modèle océanographique [Termes IGN] océanographie dynamique [Termes IGN] salinité [Termes IGN] température de surface de la mer Résumé : (auteur) General ocean circulation models are not perfect. Forced with observed atmospheric fluxes they gradually drift away from measured distributions of temperature and salinity. We suggest data assimilation of absolute dynamical ocean topography (DOT) observed from space geodetic missions as an option to reduce these differences. Sea surface information of DOT is transferred into the deep ocean by defining the analysed ocean state as a weighted average of an ensemble of fully consistent model solutions using an error-subspace ensemble Kalman filter technique. Success of the technique is demonstrated by assimilation into a global configuration of the ocean circulation model FESOM over 1 year. The dynamic ocean topography data are obtained from a combination of multi-satellite altimetry and geoid measurements. The assimilation result is assessed using independent temperature and salinity analysis derived from profiling buoys of the AGRO float data set. The largest impact of the assimilation occurs at the first few analysis steps where both the model ocean topography and the steric height (i.e. temperature and salinity) are improved. The continued data assimilation over 1 year further improves the model state gradually. Deep ocean fields quickly adjust in a sustained manner: A model forecast initialized from the model state estimated by the data assimilation after only 1 month shows that improvements induced by the data assimilation remain in the model state for a long time. Even after 11 months, the modelled ocean topography and temperature fields show smaller errors than the model forecast without any data assimilation. Numéro de notice : A2019-076 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-018-1151-1 Date de publication en ligne : 12/05/2018 En ligne : https://doi.org/10.1007/s00190-018-1151-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=92190 [article]

Le CNIG et les références géodésiques / Françoise Duquenne in XYZ, n° 154 (mars - mai 2018)

Public [article]  inXYZ > n° 154 (mars - mai 2018) . - pp 44 - 45 Titre : Le CNIG et les références géodésiques Type de document : Article/Communication Auteurs : Françoise Duquenne , Auteur Année de publication : 2018 Article en page(s) : pp 44 - 45 Langues : Français (fre) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] altitude [Termes IGN] coordonnées cartésiennes géocentriques [Termes IGN] géoïde terrestre [Termes IGN] projection [Termes IGN] système de référence local Résumé : (Auteur) Après la phase de rédaction d'un rapport sur la révision du décret n°2006-272 du 3 mars 2006, un groupe de travail est constitué au sein de la commission GEOPOS du CNIG pour accompagner la mise en œuvre des nouveaux textes de loi qui en seront issus. Ce groupe de travail est présidé par Ludovic Andres (Métropole Nice Côte d'Azur/ AITF). Son objectif est d'accompagner techniquement les juristes et les utilisateurs pour son application. Numéro de notice : A2018-087 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=89461 [article]

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Height biases of SRTM DEM related to EGM96: from a global perspective to regional practice / A. Üstün in Survey review, vol 50 n° 358 (January 2018)  

Public [article]  inSurvey review > vol 50 n° 358 (January 2018) . - pp 26 - 35 Titre : Height biases of SRTM DEM related to EGM96: from a global perspective to regional practice Type de document : Article/Communication Auteurs : A. Üstün, Auteur ; R. A. Abbak, Auteur ; E. Zeray Öztürk, Auteur Année de publication : 2018 Article en page(s) : pp 26 - 35 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] Earth Gravity Model 1996 [Termes IGN] erreur systématique [Termes IGN] géoïde local [Termes IGN] géoïde terrestre [Termes IGN] hauteur ellipsoïdale [Termes IGN] MNS SRTM [Termes IGN] Turquie Résumé : (auteur) It is investigated to what extent EGM96 affects the accuracy of digital elevation model (DEM) produced from the shuttle radar topography mission (SRTM). Global and regional analysis of EGM96 compared with EGM2008 indicate that locally there are large differences distorting to the accuracy level of SRTM DEM. In the absolute sense, the overall geoid differences throughout arc-degree tiles reach −5 m in the northeast and 2–3 m in the southern parts of Turkey. A numerical investigation over the test profiles of 200–700 km length running at various directions proves that a possible vertical datum change from EGM96 to EGM2008 yields systematically more accurate height information with an improvement of up to 2.5 m. A GPS-levelling traverse of about 900 km length points out some key patterns of this recovery. Consequently, a correction for the present version of SRTM DEM should be considered in critical implementations of Earth sciences like geoid or water flow modelling, especially for areas where EGM96 shows weak performance. Numéro de notice : A2018-176 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/00396265.2016.1218159 Date de publication en ligne : 22/08/2016 En ligne : https://doi.org/10.1080/00396265.2016.1218159 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=89820 [article]

Le chemin vers un système de référence altimétrique global et unifié / Laura Sánchez in XYZ, n° 150 (mars - mai 2017) 

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A conventional value for the geoid reference potential W0 / L. Sánchez in Journal of geodesy, vol 90 n° 9 (September 2016)  

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Gravité de la Terre : des mesures aux modèles, une image de la dynamique interne / Isabelle Panet (2015)

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Global height system unification with GOCE: a simulation study on the indirect bias term in the GBVP approach / C. Gerlach in Journal of geodesy, vol 87 n° 1 (January 2013)  

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Assessment of the GOCE-based global gravity models in Canada / Elmas Sinem Ince in Geomatica, vol 66 n° 2 (June 2012)  

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Mission design, operation and exploitation of the gravity field and steady-state ocean circulation explorer mission / R. Floberghagen in Journal of geodesy, vol 85 n° 11 (November /2011)  

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Validation of GOCE gravity field models by means of orbit residuals and geoid comparisons / Thomas Gruber in Journal of geodesy, vol 85 n° 11 (November /2011)  

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Représentations en ondelettes du champ de pesanteur / Isabelle Panet in Bulletin d'information scientifique et technique de l'IGN, n° 77 (avril 2011) 

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A comparison of recent Earth gravitational models with emphasis on their contribution in refining the gravity and geoid at continental or regional scale / D. Arabelos in Journal of geodesy, vol 84 n° 11 (November 2010)  

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Combining EGM2008 and SRTM/DTM2006.0 residual terrain model data to improve quasigeoid computations in mountainous areas devoid of gravity data / C. Hirt in Journal of geodesy, vol 84 n° 9 (September 2010)  

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